Python Programming

Let’s say you have now created a large collection of useful modules, each in a separate file, all in a single folder. It would be nice to organise them into a coherent set of modules, in a nice hierarchy.

Taking the example from the official documentation, you might want to organise your audio utility library that you just created. Perhaps in a nice hierarchy.

sound/
      formats/
              wavread.py
              wavwrite.py
              ...
      effects/
              echo.py
              surround.py
              ...
      filters/
              equalizer.py
              vocoder.py
              ...

Python allows you to package a collection of modules into a package.

Packages structure Python’s module namespace by using dotted notation. It consists of modules and subpackages.

sound.formats.wavread
sound.formats.wavwrite
sound.effects.echo

To treat directories like sound as packages, you should include an __init__.py file in the directory. It can be an empty file, may contain some initialisation code, or can be used to set the __all__ variable (we’ll discuss this later).

sound/
      __init__.py
      formats/
              __init__.py
              wavread.py
              wavwrite.py
              ...
      effects/
              __init__.py
              echo.py
              surround.py
              ...
      filters/
              __init__.py
              equalizer.py
              vocoder.py
              ...

You can then import your modules.

import sound.effects.echo

Let’s say that you have a function echofilter inside echo.py. So you can use this function as in a normal module, with all the usual different variants to import the module:

import sound.effects.echo
sound.effect.echo.echofilter()

from sound.effects import echo
echo.echofilter()

from sound.effects import echo as e
echoechofilter()

from sound.effects.echo import echofilter
echofilter()

I am lazy. Can I use from sound import *?

No, unless you are willing to do some work beforehand!

You will have to explicitly tell Python what to import when it sees the asterisk *. This is done with an __all__ variable inside the correct __init__.py.

For example, we want to enable from sound.effects import * to import both the echo and surround module.

We will thus modify sound/effects/__init__.py to contain the following line:

__all__ == ["echo", "surround"]

from sound.effects import * should now import echo and surround into the namespace.

But as usual, consider whether this is a good practice!